You record the spectrum of a star and find that the calcium absorption line,whose rest wavelength is 393.3 nm,has an observed wavelength of 394.0 nm.What is the radial velocity of this star?
A) 500 km/s
B) 50 km/s
C) 5 km/s
D) 0.5 km/s

Question

Quizplus · Accepted Answer

The radial velocity of the star can be calculated using the formula:$$v = c * (lambda_o - lambda_e) / lambda_o$$where:* v is the radial velocity* c is the speed of light* lambda_o is the rest wavelength* lambda_e is the observed wavelengthSubstituting the given values into the formula, we get:$$v = 3 * 10^8 m/s * (393.3 nm - 394.0 nm) / 393.3 nm$$$$v = -500 km/s$$The negative sign indicates that the star is moving away from us.

You Record the Spectrum of a Star and Find That